The Siemens 3RB1026-1SB0 is a solid-state overload relay from the SIRIUS 3RB family, rated 3.0...12 A with Class 10 trip characteristic, screw connection, size S0, and a manual-automatic reset selector. It mounts directly onto a contactor — no separate base needed — so it saves a DIN-rail slot in the panel and keeps the motor branch compact.
The 3.0...12 A setting range covers small to medium motor loads — think fractional-hp up to about 5.5 kW at 400 V. The solid-state sensing eliminates the bimetal drift you get with thermal relays, so the trip point stays consistent across ambient temperature shifts inside the enclosure. Size S0 mates with S0-frame contactors. The screw connection accepts standard power wiring, and the manual-automatic reset selector lets you choose latching or auto-reset after a trip.